102 W.A. E. Ussher — •Post-Tertiary Geology of Cornwall. 



to us that the Earth was covered with a sheet of water of little 

 depth, from which numerous islands emerged, over which a 

 luxuriant vegetation spread. There, in the water, lived the 

 Palcsocypris and the Palcsoniscus, on the banks of the water, upon 

 the Sigillarias, lived the Phasmidee and Mantidaa, of which several 

 species have been discovered. In the interior of these islands, in 

 the earth formed of leaves, stems, and branches of plants, lived a 

 great number of Blattidce. 



The knowledge we possess of the Carboniferous period, that is to 

 say, of the plants and animals, proves to us that there was at this 

 epoch a higher temperature and intense sunlight. The presence of 

 these two insects supports this conclusion, since all the existing 

 representatives of these groups live in the open sunlight in the 

 hotter and more humid regions of the globe. 



EXPLANATION OF PLATE IV. 



Fig. 1. Protophasma Bumasii, Ch. Brong. a, head; b, antenna; a, eye; d, palpi; 



e, prothorax ; ff, first pair of legs ; gg, elytra ; hh, second pair of legs ; 



jj, third pair of legs; k, abdomen, restored; n, wing folded on itself; 



m, wing border of the second pair, restored ; rr, wings of second pair. 

 „ 2. "Wing of the second pair, restored (the letters are explained at p, 10 L). 

 ,, 3. Part of Fig. 2, twice natural size. Fig. 4. Elytron. 

 ,, 5. "Wing and Elytron of Diura Japetus, Gray, «, upper portion of wing with 



straight nerves ; b, lower portion with nerves radiating from base of wing ; 



c, elytron. 

 „ 6. Head of P. Bumasii, twice natural size ; «, prothorax ; b, head ; d, palpi ; 



e, labrum; /, eye; g, mandibles; h, antennae. 

 ,, 7. Head of Biura Japetus, Gray. Fig. 8. Half of same, twice natural size. 

 „ 9. One of the third pair of legs of P. Bumasii, twice natural size. 



II. — Post-Tertiary Geology of Cornwall. 1 



By W. A. E. Ussher, F.G.S. 



Part II. — Pleistocene Period. 



THE materials for a classification of the later Pleistocene deposits 

 of Cornwall are so voluminous that it was found impossible to 

 embody them in a single paper. Having submitted to the Geological 

 Society a general classification with such notices of the deposits as 

 seemed necessary to show the grounds whereon it was based, I 

 purpose in the following paper to complete the notices of deposits. 

 As an apology for the amount of compilation thus rendered neces- 

 sary, I must plead the object of the papers, viz. to place in one view 

 all that has been written on the subject, as references alone would 

 entail more time and trouble in looking up than many readers would 

 be disposed to concede. 



The paper is divided into the following sections : — 

 1. Oldest superficial deposits ; 2. (a) Boulder Gravels, (5) Eaised 

 Beaches, and (c) " Head." 3. Submerged Forests and Stream-Tin 

 Gravels. 4. Becent Marine and Blown Sands. 



Oldest Superficial Deposits. — From their isolated positions, and 

 evident relations to an entirely different surface configuration, the 

 gravels of Crousa Down and Crowan, and the sands and clays of St. 



1 Continued from the February Number, p. 81. 



